


Fraternizing with the Enemy

by ChaosandDancingStars



Category: Sherlock (TV)
Genre: Big Brother Sherlock, F/M, Family Drama, Moriarty as Sherlock's brother in law, Moriarty is Alive, Mycroft Sherlock Team UP, Post Reichenbach, Protective Siblings, Weddings
Language: English
Status: In-Progress
Published: 2013-05-09
Updated: 2013-06-11
Packaged: 2017-12-10 22:19:04
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 4
Words: 3,867
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/790820
Author URL: https://archiveofourown.org/users/ChaosandDancingStars/pseuds/ChaosandDancingStars
Summary: <blockquote class="userstuff">
              <p>Post- Reichenbach Fall; Both Sherlock and Moriarty faked their deaths. A few months later, everything has gone back to "normal." But everything changes when Sherlock's baby sister announces that she is getting married. And her fiancé bears a familiar face and name. Moriarty/OC, rated "T" for the time being.</p>
            </blockquote>





	1. Chapter One

**Author's Note:**

> Hi everyone. So, my friend Kim recently got me involved in the "Sherlock" fandom after months of trying. By the end of the first season, I was itching to write a fanfic for it. As much as I love Sherlock and John (total Johnlock shipper lol), I was particularly intrigued by Jim Moriarty. My bad boy complex flaring up again lol. But kind of like my "Rise of the Guardians" fanfic "the Other Half," I wanted to put someone Sherlock cared about in Moriarty's grasp. Then I thought, why not his sister? And thus, this fic was born. Anyway, I hope you enjoy this and don't judge me too harshly: I probably won't write things half as amazing as Moffat and Gatiss. Read and Review! – Kay xoxo

"Another day, another case," Dr. John Watson, M.D., thought to himself as he ran after Sherlock.

This case was particularly unpleasant. In the last four days, three bodies had been found without faces. Sherlock had already deduced that the victims had been hit with sulfuric acid, virtually melting the faces from the muscle beneath. Each victim had shown signs of having undergone plastic surgery, but the identification process was still unfinished, leaving the investigation at a bit of a standstill.

It was all Anderson's fault, or at least according to Sherlock it was. The man seemed determined to prove Sherlock wrong and, as such, was doing everything but the facial reconstructions that were necessary for the case to go any further. When the third body had been found, Lestrade had finally threatened Anderson into doing as Sherlock said or lose his job and be charged with obstructing justice. It seemed to put the fear of God into the man as nothing else had.

So here they were, still waiting on Anderson to finish the facial reconstructions and Sherlock had gotten impatient. So he had posted a message to the culprit on his webpage and took Watson out to hunt, or as the brilliant madman had said "gather more evidence."

Honestly, there was probably nothing more terrifying to John than a bored Sherlock. And that is what was going on right now. Sherlock had gotten bored waiting and had now gone off to create his own "entertainment." Leaving John to run after him and make sure he didn't cause too much damage to any of the "little people" the consulting detective happened to come across.

Sherlock seemed particularly excitable today; why, John had no idea. But whatever it was probably didn't bode well for some poor sod. For some reason, though, John didn't think Sherlock's anxiety had anything to do with their current case. While he did have a certain gaiety about him when on the case, he was still very serious about his work. Currently he almost resemble a child who had been told Christmas had come early.

"Come along, John," Sherlock called back. "Honestly you're so much faster when we're chasing criminals."

"What exactly are we chasing, Sherlock?" John was almost tired of this little guessing game; he had been very rudely woken this morning by the madman he called his roommate and had still gotten no explanation. The doctor was more than a little annoyed at this point.

Ever since the brilliant consulting detective had come back after faking his death, Sherlock had been like the Energizer Bunny, running all over the place, barely taking a break or breaking a sweat. Quite honestly, John was rather worried for his flat mate, but other than his usual mania being rather heightened, Sherlock didn't seem too much different after his faked fall.

"We aren't chasing today, John," Sherlock replied. "We're meeting."

"Who?"

"You'll see."

They approached the Charing Cross Hotel, Sherlock seeming to move faster and faster with each step. The duo entered the rather lavish lobby, Sherlock seeming to take in every elevator at once. John didn't think he had ever seen him so antsy before; the rather tall man kept muttering to himself

"She's late, she's late." After another couple of minutes, the muttering got a bit louder.

"Ugh, she's late! She's _never_ late!"

"Who's late?" A feminine voice sounded behind the two flatmates. Sherlock's eyes seemed to brighten as he turned.

A lovely brunette was standing behind them, looking smart in a little black dress. Her feet were encased in a pair of simple black pumps and a black coat was hanging on her shoulders. Her brown eyes glittered in amusement as she took in the infamous Sherlock Holmes.

"Anna." Sherlock greeted, a rare smile crossing his face.

"Hello, brother."


	2. Chapter Two

**Summary for the Chapter:**

> Sherlock and Anna get reacquainted and Anna has a bit of a surpise.

**Notes for the Chapter:**

> So Moriarty will appear( in a way) in this chapter, if anyone was upset that he wasn't in the first one. But these things have their own times, lol. Thank you to everyone who reviewed and I hope you enjoy. –Kay xoxo

"Brother?" John questioned. "Don't tell me that you neglected to tell me about another sibling."

"John Watson, right?" Anna extended her hand. "Annaleth Rose Holmes, younger sister to Sherlock and Mycroft. Pleasure to finally meet you."

"Let me guess: you have a surveillance team following me as well, Anna?" Sherlock asked slyly, before going over to hug his baby sister.

Anna laughed. "Not at all, dear brother. I don't have Mycroft's resources after all."

"So how long have you been on holiday, Anna?" Sherlock asked, knowing she had waited to visit himself and, eventually, Mycroft.

"Oh the better part of two months," she replied, smiling. "I'd have gone back to work sooner, but it seemed a bit awkward to go back before the wedding."

"Oh, you're getting married," John said, smiling. "Well, then congratulations are in order."

"Thank you, John," Anna replied graciously. "I am quite excited for it."

"So who is this mystery man who snared my sister's heart?" Sherlock asked, seemingly innocently. He took in the rather expensive looking diamond ring on her finger; obviously her fiancé was well-off. "And when exactly where you going to introduce him to the family?"

She laughed again. "Well after the wedding, obviously. You and Mycroft would never approve; I'm not naïve, Sherlock. If the two of you had gotten your way, you both would have locked me away like a princess in a tower. No man I chose would ever measure up to your impossibly high standards. I shudder to think what you look for in a woman for yourselves."

"Hence why I will never get married," Sherlock quipped. "Besides, you glossed over who this fiancé is, Annaleth. Trying to avoid the subject, dearest sister?"

"Oh you'll find out who he is soon enough, brother," Anna smirked. "I never have anything to hold over your head that you don't already know about. Let me have my fun first."

The trio walked over to the hotel café, settling down for some coffee. Sherlock got his usual black with two sugars, John, a nice cup of tea and Anna ordering her usual Crème Brule latte.

"So Anna," John asked, cutting in before Sherlock could ask about her mysterious fiancé again. "you mentioned eventually going back to work. What do you do? Detective work like your brother, perhaps."

Anna laughed, a soft, tinkling sound that was rather lovely to John's ears. Sherlock didn't crack a grin, his eyes still taking in every nuance about his sister.

' _Her hair is down, pulled back only slightly in the back, indicating that she isn't going anywhere particularly special. However, she is wearing makeup and jewelry, so she must be meeting this fiancé at some point. She is dressed in 'work clothes' so she must be meeting him in a professional setting, possibly at his place of employment. He must work in the city, then, which narrows the radius of the search quite a bit. More information is needed, however, to make a solid hypothesis on the identity of this man.'_

"Oh no, John. I work as… well I suppose you could call me an appraiser," she said after a moment's thought. "I work with just about every medium: art, jewelry, weaponry, you name it. Which reminds me. Sherlock, why didn't you call me about that Vermeer painting last year? You could have solved it much faster if you had; you know how quickly I can spot a fake."

"It didn't cross my mind, Anna." The consulting detective replied. She did have a point, but quite honestly Sherlock didn't relish the idea of calling his baby sister when he got stuck. It seemed like such a Mycroft thing to do and Sherlock was not Mycroft.

"Oh yes it did, dear brother," Anna said, a knowing look in her eyes. "You just didn't want to run to your younger sibling to help you like our lovely elder brother. I know you Sherlock; you try to run from anything that puts you on Mycroft's level because you think yourself above him. Not that I'm one to talk."

"Yes, you despise him, don't you sister?Or has that changed in past months?"

Anna laughed again, shaking her head. John was struck again by how similar the two siblings were, not just in appearance but in mannerism.

Suddenly "Bittersweet Symphony" began playing. John looked around for the source before seeing Anna reach into her purse and pull out her cell phone. Sherlock snuck a peek at the caller i.d. All it said was "J."

_'Must be the fiancé she is trying to keep secret. Seems the cat is out of the bag now, sister mine.'_ Sherlock thought.

Anna answered the phone with a wide smile. "Hello, James."

"Hello, darling." The voice of Jim Moriarty greeted from the phone's speaker. "Enjoying your holiday?"


	3. Chapter 3

**Summary for the Chapter:**

> Sherlock and John find out who Annaleth's fiance is and the reaction isn't exactly joyful.

**Notes for the Chapter:**

> So here is chapter three. I am going to apologize in advance for any OOC-ness throughout this fic. Particularly with Sherlock in this chapter; but he is finding out about his sister’s relationship with Jim, so I figured he might lash out just a bit. Not to mention he is a difficult character to get into the mindset of. Also I will try my best to keep Anna from being a Mary- Sue; characters like that annoy me. Read and Review please! P.S: Sherlock, John and Mycroft all call Jim “Moriarty” while Anna calls him “Jim.” Just in case it gets confusing. – Kay xoxo

John and Sherlock didn’t speak. They didn’t move. They barely breathed.

It wasn’t possible. The voice on the other end of the phone couldn’t be who they thought it was. Jim Moriarty was dead; Sherlock had seen him shoot himself in the head. Moriarty was clever but was he truly that clever? And if he was still alive, what was his new plan? What did Annaleth have to do with it?

Anna noticed the boys’ sudden cessation of motion, but didn’t comment on it as she responded to Jim’s question.

“Oh I’m having a wonderful time, Jim. Of course I’d have an even better time if you were on holiday as well. You never seem to take a break. Where are you now?”

“Look behind you.”

Sherlock’s eyes narrowed, locking on the man walking up behind Anna in a dark Westwood suit. Anna turned around in her seat, a smile lighting her face as Jim Moriarty sat next to her. Neither Sherlock nor John could quite believe their eyes as the consulting criminal took her hand.

“You’re early,” Anna smiled.

“Are you complaining, love?” Jim quirked an eyebrow.

“Not at all.”

Sherlock nearly jumped out of his seat when he saw Anna lean forward and kiss Jim firmly on the mouth. He actually did when Moriarty wrapped his hand about the back of her neck and deepened the kiss.

Annaleth broke away from her lover at the sound of the table jolting, her eyes locking on her brother. She almost gulped before drawing back the infamous “Holmes-composure.” She had never seen her favourite brother so livid before. Mycroft yes; Anna and Mycroft had quite the rocky relationship and she always knew just how to wind him up. But Sherlock had only gotten angry with her once before and never this much. He’d gotten frustrated with her before, yes, but that was completely different. Sherlock looked as though he was out for blood.

“Sherlock?”

“What the devil is going on here?” he almost hissed at the couple.

“Honestly, Sherlock, if you can’t figure it out, you must be getting rusty,” Jim responded, rolling his eyes. He wasn’t thrilled that his faking of his death was now revealed to the sleuth, but Annaleth had wanted to see her brother and Jim had wanted to spend time with Anna.

“Sherlock, he’s my fiancé.” Anna said, shooting a look at Jim. As much as she loved his sass, now was not really the best time for it.

“Well isn’t this a shock?” The angry and rather betrayed detective replied. “The Consulting Criminal and the Holmes Sister set to wed. It paints an interestingly domestic picture of you Moriarty; I thought you despised all things ordinary.”

“Perhaps,” Moriarty answered coolly. “But I suppose I can handle a bit of domesticity in my life. It is surprisingly enjoyable, once you’ve found the right person. And indeed, I’ve found the right person, Sherlock. Your sister is quite the remarkable woman, in more ways than one,” the dark haired man implied with his trademark smirk.

Sherlock seemed about to take action against Moriarty when John finally intervened. He had no love lost toward the other consultant, but the last thing John needed was for Sherlock to cause even more of a scene than he already had.

“Sherlock, please,” the doctor soothed. “Not here.” People were already looking at them oddly.

The tall man sat back down stiffly, his eyes still staring accusingly at Annaleth. The woman in question took the stares head on, seemingly uncaring of the way her brother was looking at her. But under the table, her hand tightened around Jim’s, which then squeezed her own slightly, rubbing a finger over her engagement ring.

“So how exactly did this all start?” Sherlock interrogated. “When did you two meet? After I revealed that I hadn’t died or were you two having dinner while I was playing Moriarty’s games?”

“We met before you even knew of Jim’s existence Sherlock, and it’s not like it happened right away. We didn’t start seeing each other until almost a year ago. Honestly, you are blowing this out of proportion,” Anna retorted rolling her eyes.

“No, sister, I don’t believe I am,” Sherlock said lowly. “So how long did it take you to come up with this little game, Jim? Clever really, using my sister to start us off this time, but then you always were. The Richard Brook act was very convincing to the ordinary people.”

“Oh, Richard Brook was real,” Moriarty revealed slyly. “Perhaps his name wasn’t, but the man very much was. It was almost too easy to lure him into our game. Even easier to manipulate him into giving his most notable performance to date. Tricking the great Sherlock Holmes into believing his greatest enemy had shot himself. You fell for it so easily, Sherlock; quite disappointing really.” Moriarty’s eyes narrowed slightly. “And I’m not using your sister for anything. She is quite safe from our playtime.”

“Jim, stop needling him.” Anna asked. This was not going well, not that she had imagined that it would have. She had known that Sherlock would probably not accept her relationship with Jim, but she had wanted to tell him and hope that they could at least have a civil conversation. At least John was behaving, but then again he wasn’t saying much of anything at all. “Sher if it makes you feel better, I knew who he was right away. Trust me, it took a long time for us to get together. I wouldn’t just jump into bed with someone you hated all willy nilly.”

“So you knew each other before Sherlock knew him,” John inquired, sensing the consulting detective was about to lose his head. “I thought you said you were an appraiser.”

“Oh I am,” Anna reassured smoothly. “I just don’t always deal in, shall we say, entirely legal appraisals at times.”

“Much to my and Mycroft’s perpetual chagrin,” Sherlock responded, eyes still locked on Anna and Moriarty. It wouldn’t surprise anyone to note that Sherlock did not trust Moriarty. And now that Anna was involved, he trusted the slightly shorter man even less. One thing was certain: Sherlock would not be taking this “marriage” farce at face value. Somehow he needed to figure out Moriarty’s game with Anna and stop her from marrying the sociopathic criminal. And he would, one way or another.

But this was one of the rare occasions when the great Reichenbach hero would need help. And he knew just the person, as much as it pained him. Mycroft Holmes. 


	4. Chapter 4

**Summary for the Chapter:**

> Jim and Anna discuss the reveal of their relationship. John and Sherlock plan for a visit from Mycroft.

Chapter Four

It was late when Anna finally joined Jim on the couch. She had her hair pulled up to avoid dripping water on his button down. She curled up against Jim, who was going over some sort of plan on his laptop. His arm moved up to allow her to rest against his chest before placing his hand on her silk covered thigh.

The Holmes sister closed her eyes as she nestled into his warmth, sighing as Jim's lips pressed against her damp hair. His long fingers tapped a discordant rhythm on her thigh, his dark eyes remaining locked on the computer screen. She "hmm-ed" as she wrapped an arm comfortably about him, his designer cologne filling her nose with its musky aroma.

"Just a few more minutes, darling," Jim's voice sounded overhead.

"Mmmm, take your time," she replied smiling. "I'm quite comfortable."

"I can tell." And another kiss was bestowed upon her head.

A short time later, Jim closed down the laptop and set it off to the side. He stretched out his legs and wrapped his other arm about Anna, bringing her closer to his body. Silence reigned in the room for a moment before Jim finally asked.

"What is worrying you, love?" He had read the residual tension in her body as it rested against his own. As relaxed as his girl was, something was bothering her deep in that pretty little mind of hers, so much so that her body, which was normally as poised and controlled as her brothers', was reacting to it and gradually tensing up more and more.

Anna sighed. Of course Jim would figure it out; he was damn near as clever as her beloved brother. Speaking of whom…

"I'm just worried about how Sherlock is handling everything," she finally revealed. "He didn't exactly react well to it. I mean, we did metaphorically drop a bomb on him in the café, but… I don't know. I just don't want to end up losing my brother because I happened to fall in love with his nemesis."

Of course. It was her brother that was bothering her, Jim thought, a bit petulantly. It was astounding how much she admired the middle Holmes. Jim knew that Sherlock was a bit of a hero in Anna's eyes, mostly because he hadn't been like Mycroft and had actually let himself care for the only Holmes daughter. But still, it was somewhat irritating to the consulting criminal, who had always like having the attention solely upon himself.

"I'm sure it will turn out," he soothed. "Eventually they'll have to accept it, won't they?"

"Or they'll just cut me off." The words were a mere whisper.

"They wouldn't do that Anna," Jim tried to assure her, but Annaleth wasn't having any of it.

"Wouldn't they?" She sat up and faced Jim. "My icy eldest brother and the one convinced he has no heart wouldn't cut off their wayward younger sister who has fallen from grace into the arms of the man they hate?"

"Are you regretting it?" His eyes turned away from her, unwilling to let her see his weakness in that moment. He didn't wish to see her face as she told that him that all of it was a mistake, that they were a mistake.

Pale and delicate hands gently turned his face back to hers. Softness had replaced the worry and tension on Annaleth's face as she moved one her hands back down to rest upon Jim's chest.

"No, love. I don't regret us. I just wish we had done all of this before you and Sherlock started your games. Then they couldn't really do a whole lot about it. Although," she mused, "knowing my brothers, particularly Mycroft, they'd probably figure something out."

Jim laughed slightly with her in agreement before becoming serious once more.

"I don't regret anything I've done in the past, Anna," he said. "It isn't in my nature. I don't feel bad for any of the horrible things I do. But I am regretful of how the next few months will affect you."

"Just don't kill them," she replied leaning back into him. "Not even Mycroft. We may have our issues, but we're still family. I don't want to lose them, for real or otherwise."

"I'll try my best, darling," Jim promised, sealing the deal with a kiss.

-Line Break-

That same moment found Sherlock pacing the floors of 221B Baker Street in frustration. The faceless murder case had been solved fairly easily after Anderson had managed to do his job. Thus, Sherlock was left alone with his thoughts; always dangerous.

Currently those thoughts were centered around his baby sister and her involvement with Jim Moriarty. He was missing something important, he knew he was. Sure Annaleth had been in some illegalities, but they had never been as terrible as Moriarty's various misdeeds.

Finally John could take it no longer.

"Sherlock could you please sit down? You're driving me mad with all of that pacing."

Sherlock leaped over the back of his chair and sat down on it in his usual manner. John sighed as he once more viewed Sherlock's complete lack of regard for furniture.

John went back to blogging about the faceless murder case, his focus returning now that Sherlock wasn't distracting him with the pacing.

Then the tapping started.

Sherlock's long, slender fingers were tapping against the arm of the chair with no particular rhythm to it. John tilted his head back slightly in resignation before saving the draft and closing his laptop.

The consulting detective looked up as his blogger leaned forward towards him.

"Do you want to talk about it?"

"Talk about what?" Sherlock asked, poker face perfectly placed.

"Your sister and Moriarty."

"Not particularly, no."

The answer was brusquely given in typical Sherlock fashion, but John had been around him long enough to know the subtle nuances of it. He may not want to talk about it, but it was obvious he needed to.

"Are you going to warn Mycroft in advance or let him be as taken off guard as we are?" John asked with a little laugh, mischief in his eyes. Personally, he was inclined toward the latter; it was a rare occasion when one managed to shock the Iceman.

Sherlock didn't laugh. Instead he took out his phone and pressed a few buttons on it.

"I already texted him. Knowing Annaleth it could be days before she actually tells him about her association with Moriarty. Not strange considering Anna holds a rather intense dislike of Mycroft." Sherlock smiled for a moment before becoming serious once more. "But we don't have time for her to wait. We need to figure out how to get her away from Moriarty. It's only a matter of time before he puts whatever plan he has into action."

"You really care for her don't you, Sherlock." John said. "I don't think I've ever seen you so worried before. Even when Mrs. Hudson got hurt, you weren't terrible worried, at least not externally. You may have beat the living hell out of the man responsible, but you certainly weren't like this."

"She's my baby sister, John," the genius stated, as if it was obvious. "Harry may be older than you, but you'd still do anything for her. Any idiot could see that, especially considering how you've stuck by her through her drinking problems. Also, you may want to keep your phone on and charged; I expect she'll be back at the bottle soon."

John rolled his eyes derisively before getting up. He headed toward the kitchen and began the slight obstacle course of making tea.

"What are you doing?" Sherlock asked, observing his flatmate's actions.

"I don't need to be as smart as you to know that Mycroft is on his way," John replied with a smirk. "Might as well have tea ready for when he gets here."

Sherlock laughed before getting up.

"Shall I get some biscuits? I do love messing up his diet."


End file.
